I made this same comparison for Mancini a week or two ago too. The Skjei one is really interesting. I think there may be more offense available for a good skating d-man who can get pucks to the net effectively at the NHL level over college.
When Mancini started in Hartford I was expecting he'd do fairly well on the things that were his strengths in college because he was a top notch defender with a lot of size and who skated well. For a defenseman just having those specific elements in your game is enough to become an NHL player. I wasn't expecting him really to put up any offense and the 3 assists in 7 regular season games and 3 more assists in 10 playoff games was more that I would have thought.
Sometimes just playing with better players makes a player a significantly better player.
As for his chances to break camp with the Rangers I think it's still too early to tell....not just for him but for Edstrom, Othmann, Berard as well. It's one game---if he continues to stand out when he plays he'll make it hard to send him down. I'd note what Rod Brind'amour said about Seth Jarvis when he first made the Canes. That they were expecting to send him back to the CHL but his play kept him hanging around and eventually he beat out his competition and won a job. The same could happen anywhere....and there are guys I think that most people have pencilled in that could be moved for other assets if someone like a Mancini or a Berard pushes them out.